The invention is based on a hydraulic brake system having an anti-skid and traction control apparatus for motor vehicles defined hereinafter.
A brake system is known (German Patent Application P No. 40 34 113.5 published Apr. 30, 1992) in which the shutoff valve and the pressure limiting valve are embodied structurally independently of one another. The pressure limiting valve disposed parallel to the shutoff valve becomes operative if the consumer (wheel brake) cannot take the pressure fluid, fed into the line (brake line) by the pressure source (high-pressure pump) when the shutoff valve is closed. To prevent damage from an impermissibly high pressure increase in the line and in the pressure source, the pressure limiting valve opens at a predetermined response pressure, so that some of the pressure fluid can flow out to the pressure generator (master brake cylinder). The pressure limiting valve, embodied as a seat valve, executes a very small stroke in this process. This stroke is inadequate to make the pressure limiting valve open for the passage of foreign bodies entrained by the pressure fluid, such as material rubbed off from seals or metal and the like; that is, the foreign bodies become deposited on the valve seat and impair the function of the pressure limiting valve.